#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <unistd.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <string>
using namespace std;

#define COMMAND_SIZE 1024
#define FORMAT "[%s@%s %s]#"

//shell自定义的全局变量
#define MAXARGC 128
char* g_argv[MAXARGC];
int g_argc = 0;


const char* GetUserName()
{
    const char* name = getenv("USER");
    return name == NULL ? "None" : name; 
}

const char* GetHostName()
{
    const char* hostname = getenv("HOSTNAME");
    return hostname == NULL ? "None" : hostname;
}

const char* GetPwd()
{
    const char* pwd = getenv("PWD");
    return pwd == NULL ? "None" : pwd;
}

std::string DirName(const char* pwd)
{
#define SLASH "/"
    std::string dir = pwd;
    if(dir == SLASH)
    {
      return SLASH;
    }
    auto pos = dir.rfind(SLASH);
    if(pos == std::string::npos)
    {
      return "BUG";
    }
    return dir.substr(pos + 1);
}

void MakeCommandLine(char cmd_prompt[],int size)
{
    //snprintf(cmd_prompt,size,"[%s@%s %s]#",GetUserName(),GetHostName(),GetPwd());
    //snprintf(cmd_prompt,size,FORMAT,GetUserName(),GetHostName(),GetPwd());
    snprintf(cmd_prompt,size,FORMAT,GetUserName(),GetHostName(),DirName(GetPwd()).c_str());
}


void PrintCommandPrompt()
{
    char prompt[COMMAND_SIZE];
    MakeCommandLine(prompt,sizeof(prompt));
    printf("%s",prompt);
    fflush(stdout);
}

bool GetCommandLine(char* out,int size)
{ 
    char* c = fgets(out, size,stdin);
    if(c == nullptr)
    {
       return false; 
    }
    //去掉\n
    c[strlen(out) -1] = 0;
    if(strlen(c) == 0)
    {
       return false;
    }
    return true;
}

//命令行分析 "ls -a -l" -> "ls" "-a" "-l"
bool CommandParse(char* commandline)
{
#define SEP " "
    g_argc = 0;
    g_argv[g_argc++] = strtok(commandline,SEP);
    while((bool)(g_argv[g_argc++] = strtok(nullptr,SEP)));
    //会多一个减掉
    g_argc--;
    return true;
}

void PrintArgv()
{
    for(int i = 0;g_argv[i];i++)
    {
      printf("argv[%d]->%s\n", i,g_argv[i]);
    }
    printf("size = %d\n", g_argc);
}

int Execute()
{
    pid_t id = fork();
    if(id == 0)
    {
        //子进程执行
        execvp(g_argv[0],g_argv);
        //程序替换后面的程序就不执行了
        exit(1);
    }
    
    //父进程等待
    pid_t rid = waitpid(id,nullptr,0);
    //取消报警
    (void)rid; 
    return 0;
}

int main()
{
    while(1)
    {
      
      //1.打印提示信息
      //printf("[%s@%s %s]#", GetUserName(),GetHostName(),GetPwd());
      PrintCommandPrompt();

      //2.获取命令行提示符
      char commandline[COMMAND_SIZE];
      if(!GetCommandLine(commandline,sizeof(commandline)))
      {
        continue;
      }

      //char* c = fgets(commandline, COMMAND_SIZE,stdin);
      //if(c == nullptr)
      //{
      //  continue; 
      //}
      ////去掉\n
      //c[strlen(commandline) -1] = 0;
      //if(strlen(c) == 0)
      //{
      //  continue;
      //}
      //打印命令行提示符
      //printf("%s\n",c);
      //printf("%s\n",commandline);
      //for(int i = 0;i < strlen(c);i++)
      //{
      //  cout << c[i];
      //}
      
      //3.命令行分析
      CommandParse(commandline);
      //PrintArgv();
      
      //4.执行命令
      Execute();
    }
    return 0;
}
